This is a proposal for a multidisciplinary study of cardiac and skeletal muscle. Nine scientists intend to pool their interests and special skills in a series of joint projects to explore some factors controlling cell function. These include contractile protein synthesis during normal growth and in response to work stress, biochemical and physiological steps in force development, cell structure and its relation to membrane electrical properties, ionic activities in the sarcoplasm and their relation to cellular electrical and chemical function, and mitochondrial properties during growth. Various tissues will be used in the experiments, but always with the goal of understanding heart or skeletal muscle cells. Pertinent disease problems related to the work include cardiac hypertrophy, heart failure, abnormal cell growth, cardiac arrhythmias and drug effects on cell function. In addition to pooling their talents, the group of investigators wish to share certain laboratory resources including tissue culturing, electron microscopy, ion analysis by atomic absorption spectroscopy, and shop facilities. Although they are associated with four Departments, the investigators have worked together in the past, and they propose increased intellectual interaction under the auspices of this common program. All laboratories needed are already established independently, and some of the present research support will be replaced by this Program Project.